1. Field of the Invention
The present invention relates to an electronic device testing apparatus for testing semiconductor integrated circuit devices (hereinafter abbreviated as "ICs") and other electronic devices, more particularly relates to an electronic device testing apparatus able to prevent condensation on the printed circuit board easily occurring during the application of a low temperature and the radiation of heat from a socket easily occurring during the application of a high temperature or low temperature.
2. Description of the Related Art
A handler of an IC chip testing apparatus or other electronic device testing apparatus conveys a large number of IC chips held on a tray into it, brings them into electrical contact with a test head in a state with a high temperature or low temperature thermal stress applied, and has them tested at the IC testing apparatus. When the tests are completed, the IC chips are conveyed out from the test head and reloaded on trays in accordance with the results of the test so as to sort them into categories such as good chips and defective chips.
The handlers of the related art may be roughly classified by type of application of temperature into chamber type handlers which reload IC chips to be tested on a special tray called a "test tray", convey it into a temperature application chamber to bring the IC chips to a predetermined temperature, then push the IC chips against the test head in the state loaded on the test tray and heat plate type handlers which load IC chips on a heat plate (also called a "hot plate") to apply a high temperature thermal stress to them, then pick up several of the IC chips at a time by suction heads and convey them to the test head against which they are pushed.
In both types of handlers, the test head against which an IC chip is pushed is provided with an IC socket having contact pins and one or more printed circuit boards (mother board, daughter boards, subboards, etc.) electrically connected to the IC socket. The printed circuit boards are connected to input-output terminals of the test head. The IC chip is tested by the testing apparatus through the test head.
When applying a high temperature or low temperature thermal stress in a chamber type handler, however, while the IC chip is given a high temperature or low temperature in the chamber, when the IC chip is brought into contact with the IC socket, the heat is dissipated from there and therefore the problem arises of a fluctuation in the applied temperature during the tests. In particular, in a test head of a type directly connected to the IC socket and mother board and other printed circuit boards, the heat conducted to the IC socket is easily radiated to the printed circuit boards. When applying a low temperature thermal stress, further, condensation occurs at the printed circuit boards and therefore there is a danger of detrimental effect on the signal characteristics.
Also in a heat plate type handler, while the IC chip is given a high temperature, when the IC chip is brought into contact with the IC socket, the heat is dissipated from there and therefore the problem arises of a fluctuation in the applied temperature during the tests in the same way.
Also in a test head of a type where a spacing frame is arranged between the IC socket and thee print circuit board, when the IC chip is given an extremely low temperature stress of about -50.degree. C., the low temperature conducts through the coaxial cable and the daughter board connecting the IC socket and the print circuit board and therefore there is a danger that condensation occurs at the printed circuit boards.
Further, in a testing apparatus testing an IC chip inside a chamber in this way, since the chip mounting opening of the socket in which the IC chip is mounted faces inside the chamber and the terminals of the socket are connected to the test head through a printed circuit board outside the chamber (performance board), the structure is one susceptible to entry of outside air behind the socket. Therefore, there is the problem of a susceptibility to condensation at the printed circuit board behind the socket or the test head. If condensed moisture flows to electrical contact portions, there is the danger of causing short-circuits at the electrical wiring. Therefore, condensation must be prevented at all costs.
Accordingly, in the testing apparatuss of the related art, a large distance was set between the socket and the printed circuit boards and a spacing frame or other heat insulating structure was arranged between them to prevent condensation at the printed circuit boards behind the socket and the test head.
If a large distance is set between the socket and the printed circuit boards in this way, however, the electrical path from the socket to the printed circuit boards (electrical cables etc.) becomes longer and noise more easily occurs, so the reliability of the tests is liable to drop. Further, it is not possible to use general purpose printed circuit board holding rings and other parts and it is necessary to prepare special spacing frames and other heat insulating structures, so the manufacturing costs rise.